Search found 52 matches

by Jason Liu 1C
Sat Mar 17, 2018 3:12 pm
Forum: General Rate Laws
Topic: 15.49
Replies: 2
Views: 256

Re: 15.49

Yes, you can just write all the reactants into the rate law. If there are two of the same molecule in the reactants, then you will know it's second order.
by Jason Liu 1C
Sat Mar 17, 2018 1:03 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation power
Replies: 1
Views: 66

Re: Oxidation power

From what I got on my test, it seems like the more positive the reduction half reaction was, the greater the oxidation power.
by Jason Liu 1C
Mon Mar 12, 2018 12:29 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Equilibrium constant
Replies: 3
Views: 274

Re: Equilibrium constant

For a multistep reaction, you just multiply the rate constants of each forward reaction and divide it by the product of the rate constants of each reverse reaction. So K = (k1 x k2)/(k'1 x k'2)
by Jason Liu 1C
Sun Mar 11, 2018 11:01 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: k and Ea
Replies: 4
Views: 210

Re: k and Ea

The larger the value of k is, the faster the rate. If Ea is large, more energy is required for the reaction to occur, which means the rate will be slower. If the rate is slower, k will be smaller.
by Jason Liu 1C
Sun Mar 11, 2018 1:42 am
Forum: Second Order Reactions
Topic: Half life of second order reactions
Replies: 8
Views: 526

Re: Half life of second order reactions

I would still study the half life of second order reactions and understand how they work because it was on the homework and was on my test as well. I think it'd be a good idea to study it in case it's on the final.
by Jason Liu 1C
Sun Mar 11, 2018 12:25 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: entropy of vaporization
Replies: 1
Views: 250

Re: entropy of vaporization

I'm assuming you're talking about a problem asking for the entropy of vaporization at a temperature lower than the boiling point. Since you can't directly find the entropy of vaporization when the temperature is lower than the boiling point, you need to find the entropy of vaporization at the boilin...
by Jason Liu 1C
Mon Mar 05, 2018 1:51 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: slowest step determines rate of overall reaction
Replies: 3
Views: 133

Re: slowest step determines rate of overall reaction

The slowest step determines the rate of the overall reaction because other intermediate steps need the products of the slowest step to continue on with the reaction. These other steps may be faster, but they can only go as fast as the slowest step, which is why the rate of the overall reaction is de...
by Jason Liu 1C
Sun Mar 04, 2018 10:59 pm
Forum: First Order Reactions
Topic: half-lives
Replies: 4
Views: 167

Re: half-lives

I think half lives are just a convenient way of comparing the speed of reaction between reactions. You can just refer to the half lives of different reactions to see which occurs at a faster rate.
by Jason Liu 1C
Mon Feb 26, 2018 4:04 pm
Forum: General Rate Laws
Topic: Unique Rate [ENDORSED]
Replies: 4
Views: 163

Re: Unique Rate [ENDORSED]

Yes, the equation at the bottom of page 613 takes into account the coefficients and signs (positive or negative) of reactants and products in each reaction, so you should be getting the same unique rate whether you use reactant or product.
by Jason Liu 1C
Mon Feb 26, 2018 12:57 am
Forum: General Rate Laws
Topic: rate law for forward and backward reaction
Replies: 2
Views: 76

Re: rate law for forward and backward reaction

We are looking to find the rate of reaction immediately after the reaction starts. This means that none of the reactants have turned into product yet, which is why we can focus only on the forward reaction. Once there is product causing the reverse reaction, it is hard to find the rate of reaction. ...
by Jason Liu 1C
Sat Feb 24, 2018 10:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic cell set up
Replies: 8
Views: 220

Re: Galvanic cell set up

Usually the cathode is on the right in a cell diagram, but you should find the standard potentials of each half reaction to make sure. The reaction with the more positive standard potential will be the cathode.
by Jason Liu 1C
Sat Feb 24, 2018 8:52 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: When do you need to include Pt? [ENDORSED]
Replies: 5
Views: 177

Re: When do you need to include Pt? [ENDORSED]

Pt is only used in cell diagrams when a solid is needed to for the transfer of electrons from the anode to the cathode. If there is already a solid transferring the electrons, there is no need for Pt.
by Jason Liu 1C
Mon Feb 19, 2018 11:46 pm
Forum: Balancing Redox Reactions
Topic: 14.1
Replies: 1
Views: 79

Re: 14.1

There are 2 electrons on the product side of the oxidation half reaction. There are 6 electrons on the reactant side of the reduction half reaction. When you combine the two half reactions, you need to multiply everything in the oxidation half reaction by 3 to cancel out the electrons.
by Jason Liu 1C
Mon Feb 19, 2018 11:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert conductor
Replies: 2
Views: 82

Re: Inert conductor

I think you need an inert conductor when the reactants and products of the half reaction are both gases or solids because you need a solid to transfer the electrons to make the half reaction occur.
by Jason Liu 1C
Mon Feb 19, 2018 9:46 pm
Forum: Balancing Redox Reactions
Topic: 14.5a
Replies: 4
Views: 171

Re: 14.5a

The atoms being oxidized and reduced actually aren't both present in the same molecule in the products. The oxidation half reaction is O3 --> O2 and the reduction half reaction is Br- --> BrO3-
by Jason Liu 1C
Sun Feb 11, 2018 9:37 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why is deltaG of formation 0 for diatomic molecules?
Replies: 3
Views: 1725

Re: Why is deltaG of formation 0 for diatomic molecules?

ΔS isn't 0 for diatomic molecules because there is always entropy. S is only 0 when T = 0K.
by Jason Liu 1C
Sun Feb 11, 2018 8:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.19
Replies: 3
Views: 132

Re: 11.19

I think it might be because the coefficients in the chemical equations only have one sigfig
by Jason Liu 1C
Sun Feb 11, 2018 8:38 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.83
Replies: 4
Views: 176

Re: 11.83

We are looking for K, which can be found with the equation ΔG = -RTlnK. So first we need to find ΔG. We can do that by using the equation ΔG = ΔH - TΔS. We are given the temperature, but we still need to find ΔH and ΔS in order to find ΔG.
by Jason Liu 1C
Thu Feb 08, 2018 10:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Calculating entropy of vaporization
Replies: 1
Views: 93

Re: Calculating entropy of vaporization

I don't think cooling a vapor down to under its boiling point takes away enough kinetic energy from the molecules to cause them to condense. For example, at room temperature, there is still water vapor in the air. However, a cold bottle in the room will cause the water vapor to condense on the bottle.
by Jason Liu 1C
Thu Feb 08, 2018 8:13 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.33
Replies: 2
Views: 113

Re: 9.33

I agree. Gas has a much greater entropy than liquid, so just the fact that there is no gas on the product side should be enough to show that entropy has decreased.
by Jason Liu 1C
Wed Jan 31, 2018 8:51 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Celsius or Kelvin
Replies: 5
Views: 162

Re: Celsius or Kelvin

For problems with ΔT, you can use either Celsius or Kelvin because the difference between the temperatures will be the same. However, for problems with just T, you should generally use Kelvin because that is the SI unit.
by Jason Liu 1C
Sun Jan 28, 2018 10:40 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.1
Replies: 3
Views: 133

9.1

For homework problem 9.1, the solutions manual says to use the temperature in Kelvin instead of Celsius, but it was given in Celsius in the problem. How do I know when to use Kelvin and when to use Celsius?
by Jason Liu 1C
Sun Jan 28, 2018 9:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal Reversible
Replies: 3
Views: 226

Re: Isothermal Reversible

Are irreversible reactions isothermal as well? Does a change in temperature make a reaction not reversible?
by Jason Liu 1C
Sun Jan 28, 2018 9:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open, closed, or isolated [ENDORSED]
Replies: 3
Views: 216

Re: Open, closed, or isolated [ENDORSED]

The universe is an isolated system because energy cannot be created or destroyed. Likewise, matter cannot be added or taken away from the universe.
by Jason Liu 1C
Sun Jan 21, 2018 12:15 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 2
Views: 71

Re: Hess's Law

Since the intermediate steps in Hess's Law are only used to find the enthalpy of the overall reaction, the intermediate steps do not necessarily have to be able to be carried out. Therefore, it is OK to use fractions because all you need are values to calculate the overall reaction's enthalpy.
by Jason Liu 1C
Sun Jan 21, 2018 12:08 am
Forum: Calculating Work of Expansion
Topic: w=-P*deltaV
Replies: 3
Views: 131

Re: w=-P*deltaV

At a constant pressure, if volume increases, it means that the system is expanding and energy is leaving the system as work. This leaves the system with a lower internal energy. The negative sign means that when a system expand, it is losing energy as work.
by Jason Liu 1C
Mon Jan 15, 2018 9:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 8.29
Replies: 5
Views: 178

Re: Homework 8.29

I think it has more to do with how many atoms are in each molecule
by Jason Liu 1C
Sun Jan 14, 2018 10:22 pm
Forum: Phase Changes & Related Calculations
Topic: Temperature during phase change
Replies: 2
Views: 95

Re: Temperature during phase change

The water is not undergoing a phase change between the melting and boiling phases. It is in its liquid state, so adding heat will increase the temperature of the water.
by Jason Liu 1C
Sun Jan 14, 2018 10:19 pm
Forum: Phase Changes & Related Calculations
Topic: Steam burning more than water question
Replies: 4
Views: 153

Re: Steam burning more than water question

I think the amount of energy is what damages the skin. And since steam has so much more energy than water at 100 degrees Celsius, that damages the skin a lot more.
by Jason Liu 1C
Sun Jan 14, 2018 10:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 2
Views: 124

Re: Standard State

Something is in its standard state when one mole of it is being produced. You can put something into its standard state by dividing both sides of the chemical equation by however much you need to make the product one mole.
by Jason Liu 1C
Sun Dec 10, 2017 2:11 am
Forum: Administrative Questions and Class Announcements
Topic: Final
Replies: 3
Views: 287

Re: Final

The locations are separated by lecture time and last name
by Jason Liu 1C
Fri Dec 08, 2017 11:56 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and Ka
Replies: 3
Views: 297

Re: pKa and Ka

Ka is the equilibrium constant for the reaction, so a small Ka means there are few products, indicating a weaker acid. I think of pKa and Ka as inversely related; the smaller the Ka, the larger the pKa. So weak acid would have a small Ka and a large pKa.
by Jason Liu 1C
Sun Dec 03, 2017 2:38 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Drawing Coordination Compounds
Replies: 5
Views: 387

Re: Drawing Coordination Compounds

If there are different ligands around the metal, does it matter where I put each ligand?
by Jason Liu 1C
Sun Dec 03, 2017 1:53 am
Forum: Hybridization
Topic: Lone Pairs in Hybridization
Replies: 4
Views: 271

Re: Lone Pairs in Hybridization

Since hybridization relies only on areas of electron density, lone pairs count, but keep in mind that double and triple bonds only count as one area of electron density
by Jason Liu 1C
Sun Nov 26, 2017 9:52 pm
Forum: Naming
Topic: test 4 [ENDORSED]
Replies: 4
Views: 229

Re: test 4 [ENDORSED]

Yes, I think that's part of the test topics
by Jason Liu 1C
Sun Nov 26, 2017 9:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.43
Replies: 2
Views: 152

Re: 4.43

I think s-character refers to how much of the hybrid orbital is from the s orbital. So for example, the sp hybrid orbital would be 50% s-character, while the sp^3 hybrid orbital would have 25% s-character.
by Jason Liu 1C
Sun Nov 19, 2017 2:55 pm
Forum: Lewis Structures
Topic: Best way to start Lewis Structures
Replies: 12
Views: 468

Re: Best way to start Lewis Structures

I personally prefer drawing 1 bond between the central atom and each of the other atoms and then figuring out how many more bonds or lone pairs I need in order to have the right number of electrons
by Jason Liu 1C
Mon Nov 13, 2017 10:51 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 3
Views: 204

Re: Expanded Octets

On problem 4.11 part d, the Xe atom has 7 pairs of electrons. I was wondering how you figure out how many pairs of electrons should be assigned to an atom that can have an expanded octet.
by Jason Liu 1C
Sun Nov 12, 2017 8:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular shape vs Electron arrangement
Replies: 2
Views: 173

Molecular shape vs Electron arrangement

I don't quite understand the distinction between molecular shape and electron arrangement. What is the difference and how are they related?
by Jason Liu 1C
Sun Nov 12, 2017 8:08 pm
Forum: Lewis Structures
Topic: Shape
Replies: 5
Views: 227

Re: Shape

I think the molecular structure has to do with the atoms that make up the molecule and how the bonds and lone pairs of electrons will interact. The shape would be influenced by the structure and be based on the attractions and repulsion caused by the electrons.
by Jason Liu 1C
Sun Nov 12, 2017 8:07 pm
Forum: Lewis Structures
Topic: Shape
Replies: 5
Views: 227

Re: Shape

I think the molecular structure has to do with the atoms that make up the molecule and how the bonds and lone pairs of electrons will interact. The shape would be influenced by the structure and be based on the attractions and repulsion caused by the electrons.
by Jason Liu 1C
Sun Nov 05, 2017 4:25 pm
Forum: Trends in The Periodic Table
Topic: Comparing Cations and Parent Atom Atomic Radius
Replies: 2
Views: 237

Re: Comparing Cations and Parent Atom Atomic Radius

Yes. If you refer to figure 2.20, on page 51 you can see that the atomic radius of Ba is 217 pm. In figure 2.22 on page 52, it shows that Cs+1 has an atomic radius of 167 pm.
by Jason Liu 1C
Sun Nov 05, 2017 3:20 pm
Forum: Lewis Structures
Topic: Biradical vs Lone Pair
Replies: 3
Views: 149

Re: Biradical vs Lone Pair

Biradicals have two unpaired electrons, meaning each electron is in a different orbital. An atom with a lone pair has two electrons in the same orbital.
by Jason Liu 1C
Sun Oct 29, 2017 8:36 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Two multiple choice questions I was stuck on ...
Replies: 2
Views: 215

Re: Two multiple choice questions I was stuck on ...

The correct answer for 16 is C. Since Heisenberg's Indeterminacy Equation is (uncertainty of momentum) x (uncertainty of position) = h/4*pi, this means that uncertainty of momentum and uncertainty of position are inversely related. h/4*pi is a constant value, so if uncertainty of momentum is high, u...
by Jason Liu 1C
Sun Oct 29, 2017 8:31 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ionization Energy
Replies: 3
Views: 205

Re: Ionization Energy

Ionization energy refers to how hard it is to remove an electron from an atom. Atoms are more stable with a full shell, and metals in groups 1 and 2 have 1 or 2 extra electrons outside of their full shell. Since atoms are more stable with just the full shell, it's easier to remove the 1 or 2 extra e...
by Jason Liu 1C
Sun Oct 22, 2017 8:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: What section of the book to be on [ENDORSED]
Replies: 2
Views: 186

Re: What section of the book to be on [ENDORSED]

I think the material we've covered is up to 2.7, but it's always good to read ahead!
by Jason Liu 1C
Mon Oct 16, 2017 4:24 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer/Lyman Series [ENDORSED]
Replies: 7
Views: 365

Re: Balmer/Lyman Series [ENDORSED]

My TA said that the Lyman series comes to rest at n=1 and the Balmer series comes to rest at n=2, so I'm not quite sure what they're actually supposed to be.
by Jason Liu 1C
Mon Oct 16, 2017 4:24 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer/Lyman Series [ENDORSED]
Replies: 7
Views: 365

Re: Balmer/Lyman Series [ENDORSED]

My TA said that the Lyman series comes to rest at n=1 and the Balmer series comes to rest at n=2, so I'm not quite sure what they're actually supposed to be.
by Jason Liu 1C
Sun Oct 15, 2017 3:30 pm
Forum: Properties of Light
Topic: How to use the Rydberg Formula? [ENDORSED]
Replies: 6
Views: 358

Re: How to use the Rydberg Formula? [ENDORSED]

I don't see the Rydberg formula on the constants and equations sheet. Does that mean we will have to memorize it? I also don't quite understand why there is a negative sign in the formula En=-hR/n^2
by Jason Liu 1C
Fri Oct 13, 2017 10:36 pm
Forum: Properties of Light
Topic: Balmer Vs. Lyman
Replies: 12
Views: 755

Re: Balmer Vs. Lyman

What relationship do these series have with the elements? Do all elements have these series? Are the different series only referring to the electrons?
by Jason Liu 1C
Sun Oct 08, 2017 11:03 am
Forum: Molarity, Solutions, Dilutions
Topic: E 15 [ENDORSED]
Replies: 1
Views: 181

Re: E 15 [ENDORSED]

I think you need to first need to subtract the mass of the (OH)2 from the original mass to find what element "M" is. You'll find that the molar mass of "M" matches the molar mass of Calcium. The sulfide of this metal is calcium sulfide (CaS), and you can just calculate the molar ...
by Jason Liu 1C
Thu Oct 05, 2017 9:10 pm
Forum: Balancing Chemical Reactions
Topic: Order of Elements to Balance [ENDORSED]
Replies: 5
Views: 413

Order of Elements to Balance [ENDORSED]

When I'm balancing equations, in what order should I balance the elements?

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